1. Field of the Invention
The present invention relates generally to semiconductor devices, and, more specifically, to high efficiency thermoelectric materials based on Metal/Semiconductor nanocomposites.
2. Description of the Related Art
Semiconductor chip level bonded devices have found uses in several consumer and commercial applications. Typically, semiconductor devices are made from a single type of material, or different types of material are grown onto a substrate based on lattice matching and compatible crystalline structures. Devices manufactured from III-V materials are typically grown on gallium arsenide or other compound semiconductor substrates. These devices are difficult to integrate with electronic devices fabricated on silicon.
Thermoelectric materials are used to convert between thermal and electrical energy. The two main applications are cooling using the Peltier effect and power generation using the Seebeck effect. Generally, the potential efficiency of thermoelectric materials is determined by ZT, which is a dimensionless figure of merit given by S^2*sigma*T/Kappa, where S is the Seebeck coefficient, sigma is electrical conductivity, T is temperature, and Kappa is thermal conductivity. Generally, bulk materials have ZT≦1, with bismuth telluride being the dominant material at room temperature. Increasing ZT directly increases the efficiency of the material for cooling or power generation applications.
While bulk materials generally have ZT≦1, some bulk materials have slightly higher ZTs at high temperatures (>200° C. or 500K). For thin film materials, two groups have recently reported ZT˜2 near room temperature, and one group has claimed ZT˜3 at T=550K. In both cases, the materials are tellurides with nanostructure to decrease thermal conductivity and (possibly) increase the power factor (S^2*sigma).
There is a need, then, for materials with a high ZT for use in applications where conversion between thermal and electrical energy is desired.